The present invention relates to a seal for a pair of relatively rotatable components.
UK Patent No. 1554406 discloses a secondary seal which will provide a temporary seal under running conditions or a seal capable of holding pressure over longer periods under non-running conditions, in the event that a primary sealing device, for example a mechanical face seal, should fail.
The seal described in that patent, has an inwardly directed lip which is a close or interference fit on the rotary component, for example shaft, but is only forced into sealing engagement with the rotary component upon exposure to fluid under pressure. An outwardly directed lip is deflected to a substantial degree by engagement with the stationary component, for example a housing, to provide a permanent seal therebetween.
Because of the need to deflect the outer lip to a substantial degree, against the direction of movement of the seal as it is located between the rotary and non-rotary components, such seals are difficult to fit. Furthermore, the seal has little radial compliance and is unable to tolerate variations in concentricity between the rotary and non-rotary components.
The present invention provides an improved seal which will mitigate these problems.